Helicobacter pylori Infection

Definition

Helicobacter pylori infection is a chronic bacterial infection of the gastric mucosa caused by H. pylori, leading to gastritis, peptic ulcer disease, and increased risk of gastric malignancies.

Epidemiology

• Prevalence varies globally: high in developing countries (>70%) and lower in developed countries (<40%)
• Acquired primarily in childhood, persists if untreated
• Transmission is mainly oral-oral or fecal-oral
• Associated with low socioeconomic status, crowded living conditions, and poor sanitation
• Major cause of peptic ulcer disease and gastric cancer worldwide

Etiology

• Caused by Helicobacter pylori, a Gram-negative, spiral-shaped, microaerophilic bacterium
• Virulence factors: urease production, CagA and VacA proteins leading to mucosal injury and inflammation
• Transmission: direct person-to-person (oral-oral, fecal-oral), contaminated water or food
• Risk factors: family history of H. pylori infection, smoking, NSAID use, chronic gastritis

Pathophysiology

• Bacterium colonizes gastric epithelium and produces urease to neutralize gastric acid
• Induces chronic inflammation via host immune response and cytotoxins (CagA, VacA)
• Disruption of mucosal barrier leads to gastritis and peptic ulcer formation
• Chronic infection increases risk of atrophic gastritis, intestinal metaplasia, and gastric adenocarcinoma
• H. pylori alters gastric acid secretion, contributing to ulcer disease